<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      class Person {
        constructor() {
          this.name = "jack";
        }
        say() {
          console.log("hello");
        }
        add(a, b) {
          return a + b;
        }
      }
      class Human extends Person {
        add(a, b, c) {
          return super.add(a, b) + c;
        }
      }
      const p = new Human();
      console.log(p.add(1, 2, 3));
    </script>
  </body>
</html>
